1. Field of the Invention
The present invention relates to a recording disk drive such as a hard disk drive unit (HDD), and in particular, to a recording disk drive comprising a spindle motor for driving a recording disk for rotation.
2. Description of the Prior Art
In general, a spindle motor assembled in the HDD comprises a stator fixed to the housing base of the HDD, and a rotor mounted around the central axis fixed to the housing base. The rotation of the rotor is generated by the mutual effect between the magnetic fields induced in the stator and rotor, respectively. The rotation of the rotor causes the rotation of recording disks mounted around the rotor.
The stator comprises an annular member which allows the inner surface to contact an annular wall raised from the housing base. A plurality of core bodies are integrally formed on the annular member so as to extend in the radial directions. Coils are wound around the respective core bodies so as to induce magnetic fields in the stator. The employment of such annular member is supposed to assist the respective coils to be positioned relative to the housing base. Rough positioning of the coils leads to an eccentricity between the annular arrangements of the coils and the permanent magnets in the rotor. This is not desirable.
The rotor is in general supported around the central axis via a pair of ball bearings fixed around the central axis at upper and lower positions, respectively. It is desirable to take a larger span between the upper and lower ball bearings along the central axis. A shorter span may cause the rotor to vibrate during rotation around the central axis. If reduction in thickness of the HDD is further expected, a larger span between the upper and lower ball bearings inevitably causes reduction in height of the annular wall which contacts the inner surface of the annular member.
Higher recording density to a recording disk is still expected in the field of recording disk drives. Improvement in recording density can be realized by reduction in track pitch on a recording disk. It is inevitable to reduce vibration of the rotating recording disk in reducing the track pitch, because the accuracy in positioning a transducer head gets deteriorated if the recording disk vibrates.
When the suppression in vibration is intended in a recording disk, it is required to reduce the vibration of the operating spindle motor which drives the recording disk for rotation. However, reduction in the height of the annular wall on the housing base, as described above, tends to cause reduction in rigidity in supporting the stator, so that it gets difficult to reduce the vibration of the spindle motor.
It is accordingly an object of the present invention to provide a recording disk drive which contributes to reduction in the vibration of a spindle motor.
According to a first aspect of the present invention, there is provided a recording disk drive comprising: a central axis fixed to a housing base; a rotor mounted around the central axis for relative rotation so as to receive a recording disk; an annular member disposed in a region between the rotor and the central axis so as to be stationary to the central axis; a core body extending in a radial direction from the annular member so as to face the rotor; and a coil wound around the core body so as to provide a stator and fixed to the housing base.
With the above structure, the core body and coil, cantilevered by the annular member, are also supported by the housing base through the coil. Accordingly, the movement of the core body and coil is restrained, so that the stator can be prevented from vibrating during rotation of the rotor. Reduction in the vibration of spindle motor can reliably be achieved.
The number of coils to be fixed to the housing base can be selected depending on the frequency of vibration caused by rotation of the recording disk. Since the frequency of vibration in the stator depends on the number of coils to be fixed to the housing base, the number of coils to be fixed can be selected to vary the frequency of vibration in the stator. If the frequency of vibration in the stator can be shifted out of the frequency of vibration in the rotor, the resonance between the vibrations of the stator and rotor can be prevented. Besides, the frequency of vibration in the stator can be adjusted based on the location of the coil fixed to the housing base.
In fixing the coil to the housing base, a recess may be formed on the housing base so as to extend in a circumferential direction of the recording disk. The recess allows an adhesion poured therein to receive the coil. The adhesion serves to reliably fix the coil to the housing base when hardened. In this case, the frequency of vibration in the stator can be adjusted, not only by selecting the number of coils to be fixed or the location of the coil in the aforementioned manner, but also by varying the extent of the recess. Variation in the extent of the recess allows variation in the contact area between the adhesion and coil, so that the rigidity can be varied in supporting the stator.
In place of the recess, the recording disk drive may comprise a pedestal formed on the housing base so as to provide a receiving surface with an adhesion applied thereto. The receiving surface receives the coil. The adhesion serves to reliably fix the coil to the housing base through the pedestal when hardened. In this case, the frequency of vibration in the stator can be adjusted not only by selecting the number of coils to be fixed or the location of the coil in the aforementioned manner, but also by varying the area of the receiving surface. Variation in the area of the receiving surface allows variation in the contact area between the adhesion and coil, so that the rigidity can be varied in supporting the stator.
According to a second aspect of the present invention, there is provided a recording disk drive comprising: a central axis fixed to a housing base; a rotor mounted around the central axis for relative rotation so as to receive a recording disk; an annular member disposed in a region between the rotor and the central axis so as to be stationary to the central axis; a core body extending in a radial direction from the annular member so as to be supported by the housing base; and a coil wound around the core body so as to provide a stator.
With the above structure, the core body and coil, cantilevered by the annular member, are also supported by the housing base at the tip or free end of the core body. Accordingly, the movement of the core body and coil is likewise restrained, so that the stator can be prevented from vibrating during rotation of the rotor. Reduction in the vibration of spindle motor can reliably be achieved.
In the same manner as the first aspect, the number of core bodies to be supported on the housing base can be selected depending on the frequency of vibration caused by rotation of the recording disk. Since the frequency of vibration in the stator depends on the number of core bodies to be supported on the housing base, the number of core bodies to be supported can be selected to vary the frequency of vibration in the stator. If the frequency of vibration in the stator can be shifted out of the frequency of vibration in the rotor, the resonance between the vibrations of the stator and rotor can be prevented. Otherwise, the frequency of vibration in the stator can be adjusted based on the location of the core bodies supported on the housing base.
In particular, three of the core bodies are preferably supported by the housing base. If three core bodies are supported on the housing base, the annular member can easily be set at an attitude parallel to the housing base.
In supporting the tip end of the core body on the housing base, the recording disk drive may comprise a pedestal formed on the housing base so as to provide a receiving surface with an adhesion applied thereto. The receiving surface receives the core body. The adhesion serves to reliably fix the core body to the housing base through the pedestal when hardened. In this case, the frequency of vibration in the stator can be adjusted not only by selecting the number of core bodies to be supported or the location of the core body in the aforementioned manner, but also by varying the area of the receiving surface. Variation in the area of the receiving surface allows variation in the contact area between the adhesion and core body, so that the rigidity can be varied in supporting the stator.
In place of the pedestal, the recording disk drive may comprise a fixing pin standing on the housing base, and a pin hole formed in the core body so as to receive the fixing pin. When the pin hole receives the fixing pin, the tip end of the cantilevered core body can be supported on the housing base through the fixing pin.
The adhesion employed in the first and second aspects may have an elasticity. The employment of the elastic adhesion serves to damp the vibration in the coil or/and core body, so that it is possible to suppress the amplitude of the vibration in the stator.
A spindle motor comprising the aforementioned central axis, rotor and stator may be employed not only in a recording disk drive such as a hard disk drive unit (HDD), a floppy disk (FD) drive, a compact disk (CD, CD-ROM, CD-R) drive, a digital video disk (DVD) drive, but also in other instruments such as a video cassette recorder (VCR), a voice cassette recorder, or the like. When the spindle motor is assembled in the aforementioned recording disk drive, the recording disk drive preferably comprises an annular wall raised on the housing base around the central axis so as to contact an inner surface of the annular member.